A novel optical method and a nanometer laser system are introduced for micro displacement measurement.The improved method is based on the principle of optical lever.By using this method,the micro displacement is magnified 10~2 times.The theoretical resolving power of this system is 4 nm,and the practical resolving power is less then 10 nm,which is analyzed theoretically and proved by the experiments.The experiment results show that this system is highly accurate and sensitive even in air.This automatic measurer can be used in lots of conditions and be modified into micro-electromechanical system(MEMS) with the advantage of simple configuration.